Using ADP5520 for driving SHARP LCD backlight

Hi,

We are planning to use the ADP5520 Backlight driving chip for our LCD panel - SHARP - LQ043T3DG01. Datasheet can be downloaded from here:

http://www.google.co.in/url?sa=t&rct=j&q=sharp%20lq043t3dg01&source=web&cd=1&ved=0CDAQFjAA&url=http%3A%2F%2Fwww.sharpsme.com%2Fdownload%2FLQ043T3DG01-SPpdf&ei=5caCT6WoCpHMrQfvksHeBQ&usg=AFQjCNE8xPyTp0LW6AXB_0xxWSb0adR61Q&cad=rja

Could someone please confirm if ADP5520 can drive the backlight for the above display. The chip datasheet mentions the right voltage range needed but it also says it can support only upto 6 LEDs while this SHARP display has 9 LEDs. Should it make the difference as long as the voltage is within range?

Best regards,

Ashish

  • 0
    •  Analog Employees 
    on Apr 9, 2012 8:27 PM

    Hi Ashish,

    As far as I can see, from the SHARP documentation, the LED max forward voltage for 9 LEDs in series is 31.5V while the typ. is 28.8V, assuming 20mA driving current. The ADP5520 has an over-voltage protection circuit (OVP) set to 27V (29.5V max), this means that driving the module with 20mA the ADP5520 will likely enter in OVP where the boost circuit will be disabled until the voltage on BST pin falls below OVP limit, minus some hysteresis. In this mode of operation the LED average current will be severely limited.

    If your application allows, you can consider to decrease the LED current so that the total VF voltage for the 9 LEDs is below OVP level across temperature and lot to lot variations, this is something you will need to check with SHARP or Nichia.

    Please let me know if you need additional information. Thanks

    Best regards,

    Maurizio